1. Field of the Invention
The present invention relates to a magnetic head for perpendicular magnetic recording that is used for writing data on a recording medium by means of a perpendicular magnetic recording system, and more specifically, to a magnetic head for perpendicular magnetic recording that has a main pole and a shield, and a method of manufacturing the same.
2. Description of Related Art
The recording systems of magnetic read/write apparatuses include a longitudinal magnetic recording system wherein signals are magnetized in a direction along the plane of the recording medium (the longitudinal direction) and a perpendicular magnetic recording system wherein signals are magnetized in a direction perpendicular to the plane of the recording medium. It is known that the perpendicular magnetic recording system is harder to be affected by thermal fluctuation of the recording medium and capable of providing higher linear recording density, compared with the longitudinal magnetic recording system.
Magnetic heads for perpendicular magnetic recording typically have, like those for longitudinal magnetic recording, a structure where a read head unit having a magnetoresistive element (hereinafter, also referred to as MR element) for reading and a write head unit having an induction-type electromagnetic transducer for writing are stacked on a substrate. The write head unit includes a main pole that produces a magnetic field in a direction perpendicular to the plane of the recording medium. The main pole includes, for example, a track width defining portion having an end located in a medium facing surface that faces the recording medium, and a wide portion that is connected to the other end of the track width defining portion and is greater in width than the track width defining portion. The track width defining portion has a generally constant width. To achieve higher recording density, it is required that the write head unit of the perpendicular magnetic recording system be smaller in track width and improved in write characteristics such as overwrite property which is a parameter indicating an overwriting capability.
A magnetic head for use in a magnetic disk drive such as a hard disk drive is typically provided in a slider. The slider has the medium facing surface mentioned above. The medium facing surface has an air inflow end (a leading end) and an air outflow end (a trailing end). The slider is designed to slightly fly over the surface of the recording medium by means of an airflow that comes from the air inflow end into the space between the medium facing surface and the recording medium. The magnetic head is typically disposed near the air outflow end of the medium facing surface of the slider. In a magnetic disk drive, positioning of the magnetic head is performed by a rotary actuator, for example. In this case, the magnetic head moves over the recording medium along a circular orbit about the center of rotation of the rotary actuator. In such a magnetic disk drive, a tilt of the magnetic head with respect to the tangent of the circular track, which is called a skew, occurs according to the position of the magnetic head across the tracks.
In particular, in a magnetic disk drive of the perpendicular magnetic recording system which is higher in capability of writing on a recording medium than the longitudinal magnetic recording system, the skew mentioned above can cause the phenomenon that signals already written on one or more tracks that are adjacent to a track targeted for writing are erased or attenuated during writing of a signal on the track targeted for writing (such a phenomenon will hereinafter be referred to as adjacent track erase). To increase the recording density, it is required to prevent the occurrence of adjacent track erase.
Providing one or more shields near the main pole is effective for preventing the aforementioned skew-induced adjacent track erase and increasing the recording density. For example, U.S. Patent Application Publication No. 2009/0015965 A1 discloses a magnetic head including a return yoke that forms a magnetic path in conjunction with the main pole. The return yoke includes a return yoke tip having an end face that is located in the medium facing surface and spaced from an end face of the main pole by a predetermined distance. The return yoke tip functions as a shield.
U.S. Pat. No. 6,954,340 B2 and U.S. Patent Application Publication No. 2005/0128637 A1 disclose a magnetic head including four shields: one having an end face located in the medium facing surface at a position forward of the end face of the main pole along the direction of travel of the recording medium; another having an end face located in the medium facing surface at a position backward of the end face of the main pole along the direction of travel of the recording medium; and the other two having two end faces located in the medium facing surface at positions on opposite sides of the end face of the main pole in the track width direction. The end faces of the four shields are arranged to wrap around the end face of the main pole in the medium facing surface.
In a magnetic head, a position that is located forward of the main pole along the direction of travel of the recording medium is a position on the air-outflow-end side (the trailing end side), while a position that is located backward of the main pole along the direction of travel of the recording medium is a position on the air-inflow-end side (the leading end side). Hereinafter, a shield having an end face located forward of the end face of the main pole along the direction of travel of the recording medium will be referred to as a trailing shield, while a shield having an end face located backward of the end face of the main pole along the direction of travel of the recording medium will be referred to as a leading shield.
In a magnetic head having one or more shields, there are typically provided one or more return path sections for connecting the one or more shields to a portion of the main pole away from the medium facing surface. The one or more shields and the one or more return path sections function to capture a magnetic flux that is produced from the end face of the main pole and spreads in directions other than the direction perpendicular to the plane of the recording medium, and to thereby prevent the magnetic flux from reaching the recording medium. The one or more shields and the one or more return path sections also function to allow a magnetic flux that has been produced from the end face of the main pole and has magnetized the recording medium to flow back to the main pole. Thus, the magnetic head having one or more shields can prevent the adjacent track erase and achieve a further improvement in recording density.
The position of an end of a record bit to be recorded on the recording medium depends on the position of an end of the end face of the main pole located in the medium facing surface, the end being located forward along the direction of travel of the recording medium. In order to define the position of the end of the record bit accurately, it is therefore required that the magnetic head have a trailing shield and that the trailing shield be capable of capturing as much magnetic flux as possible.
In addition, as the frequency of the recording signal is increased for higher recording density, the magnetic head needs improvement in the rate of change of the direction of the magnetic flux produced from the end face of the main pole. To meet such a requirement, it is particularly effective to reduce the length of a magnetic path that passes through the trailing shield and the main pole.
In the magnetic head disclosed in U.S. Patent Application Publication No. 2009/0015965 A1, the return yoke tip corresponds to the trailing shield. This U.S. patent document discloses a technology for reducing the yoke length which is related to the length of the magnetic path passing through the trailing shield and the main pole. More specifically, the technology provides a coil encompassing the main pole in a solenoid structure. The coil includes a lower wire portion passing through the lower portion of the main pole, an upper wire portion passing through the upper portion of the main pole, and a connection portion electrically connecting the lower wire portion and the upper wire portion. The upper wire portion includes an upper wire layer having a stack of at least two layers.
The aforementioned technology, however, has the problem that the structure of the coil and the structure in the vicinity of the coil become complicated and a greater number of steps are needed to form the coil.
In addition, in the magnetic head disclosed in U.S. Patent Application Publication No. 2009/0015965 A1, there is a large distance between the upper wire layer and the return yoke in a direction perpendicular to the medium facing surface. That is, the magnetic path through the trailing shield and the main pole is not sufficiently reduced in length.